Surface treatment nozzle

ABSTRACT

There is described a surface treatment nozzle which generates a surface treatment jet that comprises a suspension of surface treatment material and gas and a surrounding liquid-containing jet for preventing dusting. The surface treatment jet has a high velocity compared with the velocity of solely liquid and is conveyed in an inner tube ( 13; 31 ) and the liquid is conveyed in a channel ( 12 ) between the inner tube and a tube ( 11 ) concentrically surrounding the inner tube. There is included a mixing arrangement ( 14, 15, 16; 22; 29, 30, 25 ) for mixing the liquid with gas upstream of the nozzle outlet and to impart to the liquid/gas mixture a velocity in the same order of magnitude as the velocity of the surface treatment jet at said outlet.

BACKGROUND OF THE INVENTION

Teeth are often polished with the aid of polishing nozzles that blow apolishing mixture of air and powder against the tooth to be polished.The powder is most often bicarbonate. Another gas can be used instead ofair. Jets of water that form a curtain around the powder/air suspensionare also sprayed onto the tooth to prevent dusting.

The principle developed in accordance with the invention is notrestricted solely to polishing operations, but can also be applied withother types of powder, such as Al₂O₃ for instance, to abrade a tooth inscaling an outer surface of the tooth, or can be applied instead ofconventional drilling. A small polishing and drilling nozzle may, ofcourse, also be used in contexts other than with teeth, for instance inconnection with manicures, the production of jewellery, and the like.

A number of different systems in which the aforesaid principle is usedare known to the art. For instance, U.S. Pat. Nos. 3,972,123, 4,174,571and 4,696,644 teach a tooth-polishing nozzle which includes mutuallyconcentric tubes of which the centre tube conveying the powder/airsuspension projects in relation to the outermost tube, wherein water isconveyed in a channel defined between both tubes. U.S. Pat. No.4,412,402 describes a more functional design where the centremost tubecarrying the powder/air suspension is withdrawn in relation to thewater-conveying outer tube. In addition, the faster flowing powder/airsuspension is able to entrain at least a part of the much slower waterflow, up to the orifice of the polishing nozzle.

One problem with earlier designs is that the powder/air suspension has arate of flow of about 15-20 ml/min., while only a total flow of water of5-15 ml/min. can be achieved. It will be noted that the lowest possiblewater flow is desired, so that the patient will not feel that he isdrowning in water and so that not too much water will be applied to thesurface of the tooth being polished. Powder particles will then bedeposited in the water instead of on the tooth. This means that the airvelocity v_(air) will be about 1000 to 1500 times the water velocityv_(water). Although it is true that some water will be entrained by theair in the device described in U.S. Pat. No. 4,412,402 in particular,the effect achieved therewith is in no way satisfactory. Furthermore,there is a significant imbalance between ejection of the powder/airsuspension and the water, due to the different velocities, which givesrise to turbulence and vigorous mixing between the flows.

SUMMARY OF THE INVENTION

One object of the invention is to provide a surface treatment nozzlewhich functions to eject powder/gas and a liquid-containing protectivecurtain, where said ejections have the least possible effect on oneanother.

Another object of the invention is to provide a surface treatment nozzlethat ejects powder/gas and a liquid-containing protective curtain wherebut small turbulence is obtained between the different flows.

Another object of the invention is to provide a surface treatment nozzlethat includes but few separate parts and is readily manufactured.

The invention thus relates to an improved surface treatment nozzle forgenerating a surface treatment jet comprising a suspension of surfacetreatment material and gas and a liquid-containing surrounding jet forpreventing “dusting”, wherein the surface treatment jet has a greatervelocity than the velocity of solely liquid, wherein the surfacetreatment jet is conveyed in an inner tube and the liquid in a channellocated between said inner tube and a tube that surrounds the inner tubeconcentrically. According to the invention, there is provided a mixingarrangement for mixing liquid with gas upstream of the nozzle outlet andimparting to the liquid/gas suspension a velocity of the same order ofmagnitude as the velocity of the surface treatment jet at said outlet.

The mixing arrangement will preferably include an internal outlet fromthe liquid conveying channel and discharge means for delivering part ofthe gas in the surface treatment jet, as gas for producing thegas/liquid mixture in an amount such as to impart the desired velocitythereto. The mixing arrangement may include an expansion channel for theliquid and gas mixture externally of the discharge means. The mixingarrangement will preferably include an at least internal constriction ofthe inner tube downstream of the discharge means.

The inner tube that conveys the surface treatment material/gassuspension may be circular at least at the nozzle orifice and have adiameter which provides space for a surrounding flow of the liquid/gasmixture through cavities around the orifice of the inner tube. Thecavities around the orifice of the inner tube may comprise a ring ofdrilled holes or a central irregular hole that includes wall parts whichprovide internal support for the orifice of said inner tube when saidtube is inserted in the central hole.

The inner tube (13; 31) conveying the suspension of surface treatmentmaterial and gas may have a polygonal orifice (28), e.g., an orificewith three corners, at least up to the nozzle orifice, and the nozzleorifice may have a central round hole (27) with a diameter adapted as acorner support and to provide space for a surrounding flow of liquid andgas mixture through said cavities around the orifice (28) of the innertube. The sizes and forms of the discharge means, the expansion channel,the inner constriction and the cavities through which the liquid/gasmixture exits should be balanced in relation to each other such as toachieve the best possible similarity between the respective velocitiesof the suspension of surface treatment material and gas and the mixtureof liquid and gas. The gas may be air and the surface treatment materialmay be a polishing material, for instance bicarbonate, or an abrasivematerial, for instance Al₂O₃.

Because the velocities of both ejected flows lie in the same order ofmagnitude, there is practically no turbulence between the flows at theoutlet orifice of the surface treatment nozzle. Reduced turbulenceresults in improved efficiency and also in small inter-mixing betweenthe flow areas.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the accompanyingdrawings, which are only to be considered as exemplifications of theinventive principle, wherein

FIG. 1 is an overall view of a surface treatment instrument;

FIG. 2 illustrates in perspective and partially in section a firstembodiment of a surface treatment head according to the invention;

FIG. 3 illustrates in perspective and partially in section a secondembodiment of a surface treatment head according to the invention; and

FIG. 4 illustrates in perspective and partially in section a thirdembodiment of the surface treatment head according to the invention.

Those components that find correspondence in the various Figures havebeen identified with the same reference signs.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Shown in FIG. 1 is an inventive surface treatment head 1 in which aninner concentric tube extends throughout the entire instrument. Theconcentric tubes (not shown in FIG. 1) have a curve or bend 2 close tothe head 1 in order to provide the operator with a good workingposition, i.e. for the dentist or dental hygienist in the case of dentaltreatment. The illustrated bead includes an inner hexagonal support 3for a handle (not shown) inserted over the rear part of the instrument.Means for delivering powder/gas suspension to the inner tube and liquidto the space between the concentric tubes are disposed at the rear endof the instrument. This supply is achieved with the aid of knowntechnology and constitutes no part of the actual invention and istherefore not shown. The gas is preferably air and the surface treatmentjet is hereinafter referred to as the powder/air suspension. The liquidis preferably water and is therefore referred to as such hereinafter.

According to the principle of the invention, water and air areintermixed in the surface treatment head prior to ejecting the mixturethrough openings 4 in one end of the head, in the form of a curtainaround the powder/air suspension, which is ejected as polishing agentthrough a central opening 5 in the outer end of the head 1. Therespective ejected water/air and powder/air suspensions shall havemutually the same velocities, such that one mixture shall not berequired to entrain the other mixture in order to prevent turbulence andintermixing between the flow areas. This type of arrangement provides asplendid function, since the forcibly ejected water/air mixture forms awater mist. Tests have shown that the invention functions verysatisfactorily in a highly dust-free manner.

It thus lies within the scope of the invention to deliver a water/airmixture to the outer tube right from the connection source. However,this is rather impracticable as the hose arrangement will then beclumsy. In practice, the function of the invention is improved when thewater/air mixture is delivered relatively close to the outlet orifice ofthe polishing nozzle and air contained in the powder/air suspension isused as an admixture in the water. This also enables the suspension andmixture to be given the same velocity more easily.

The embodiment shown in FIG. 2 includes an outermost protective tube 10,followed by an outer tube 11 which defines part of a water channel 12,and an inner tube 13 which functions to define a further part of thewater channel 12 and also as powder/air suspension delivery tube. Theouter tube 11 terminates at a relatively long distance upstream of thefront end of the protective tube 10. The tubes 11 and 13 lie closetogether at the rear part, such as to define therebetween a relativelynarrow water channel, said water having a low rate of flow in saidchannel, e.g., a flow rate of 5-15 ml/min. The tube 13 is provideddownstream of the end of the outer tube 11 with a number ofthrough-penetrating holes 14 which thus open into the wider channel 15defined between the protective tube 10 and the inner tube 13.

The inner tube 13 has a narrowing or tapering part 16 nearer the outletorifice, whereas the outer part retains its shape up to a short distanceupstream of the orifice at 17, where the outer diameter of said outerpart also decreases to provide a chamber in front of the end of theprotective tube 10. The protective tube 10 includes a chamber outlet atits outer end in the form of a ring of outlet holes 18 for the water/airmixture. The orifice 19 of the outer narrowing part 16 of the inner tubecarrying the powder/air suspension projects a short distance beyond theorifice part that includes the holes 18.

The through-passing holes 14 in the tube 13 are mutually of the samesize and are disposed in a ring around the tube. Although this is apractical arrangement, the holes may alternatively be disposed in someother way provided that the effect achieved around the outlet hole 19 isgenerally uniform.

The narrowing inner part 16 is intended to function as a constriction toenable air in the inner tube 13 to exit more easily through the holes 14and into the water channel 15. The wider channel 15 is intended toenable the mixture of air and water formed in said channel to expandreadily.

Thus, in the case of the inventive embodiment the powder/air suspensionis not required to entrain the water, and the air that entrains thewater is delivered to the water channel and already mixed with the airin the channel 15 upstream of the outlet. The velocities of thepowder/air suspension and the water/air mixture exiting from the surfacetreatment nozzle will lie within the same order of magnitude. Forinstance, the flow rate of the water/air mixture may be roughly 4-6l/min. (instead of roughly 5-15 ml/min. with respect to solely water),and the flow rate of the powder/air suspension may be 15-20 l/min. Therespective velocities of the powder/air suspension and the water/airmixture may be maintained in the same order of magnitude, by providingan appropriate balance between the different outlet areas 18/19, 22/23and 27/28.

Instead of a ring of holes around the orifice of the protective sleeve,the embodiment shown in FIG. 3 has an angular opening 20 from which theround tube of the narrowing part 17 projects. Although the illustratedopening 20 is shown to be hexagonal, it will be understood that thenumber of edges is can be chosen freely, the one proviso being that awater/air mist is able to exit from the region around the narrowing part17. The opening may alternatively include outwardly extending arcs tofacilitate exit of the water/air mixture. It is less expensive toprovide only one opening in the end of the protective sleeve 21 than aplurality of holes. The orifice 17 is held in place by the sides of theopening 20, against which it supports.

In the case of the FIG. 3 embodiment, the water/air mixture is ejectedthrough the generally triangular corner parts formed between the tubepart 17 and the hole 20. This embodiment also includes a simpler variantof the restriction 22 in the inner tube than in the case of thearrangement shown in FIG. 1. The tube wall does not have different innerand outer diameters anywhere along its length, and narrowing of the tubehas been achieved simply by compressing the tube externally. Althoughthis embodiment results in a slightly lower velocity of the exitingwater/air mixture, it is nevertheless fully acceptable.

FIG. 4 illustrates an embodiment in which the narrowing part 25 has beencompressed to obtain an approximate polygonal shape (exaggerated in thedrawing), which is particularly purposeful up to the orifice. Althoughthe polygonal shape in this embodiment is shown to be triangular, it mayalternatively be square, pentagonal or hexagonal and still functionwell.

The outlet opening 27 in the end of the protective tube 26 is round,which is easiest to form in a stainless steel protective tube, stainlesssteel being a preferred material in this context. In the case of theillustrated embodiment, the generally triangular orifice 28, preferablywith rounded corners, is inserted so that its corners support againstthe side of the round opening 27. The powder/air suspension flows outthrough the opening on the orifice 28, whereas the water/air mixtureflows out in the three segmental openings defined between the opening 27and the orifice 28. The outlet openings 29, 30 for the air in the innertube 31 are placed in line with each respective segmental openingparallel with the axis of the polishing nozzle. The embodiment shown inFIG. 4 has only one outlet opening on the tube 31 for each segmentalopening, although more outlet openings may, of course, be placedsymmetrically in relation to respective openings at said orifice. In theembodiment shown in FIG. 4, the triangular outlet opening for powder/airlies level with the opening 27. It will be obvious that the triangularorifice 28 may be displaced forwards and that the forwardly displacedopenings for powder/air in the aforedescribed embodiments may lie inline with the end of the polishing nozzle, similar to the FIG. 4embodiment. Alternatively, the powder/air opening may be withdrawnrelative to the end of the polishing nozzle. A protruding powder/airopening is preferred, however, since this results in the least risk ofclogging in respect of the water/air flow.

The size of the holes 14 in the inner tube 13, 31 and the outletopenings 29, 30 respectively is relatively irrelevant. The powder has aparticle size distribution of a bell curve and since the powder iscarried by the air at a high velocity and because each particle has acertain weight, it has been found that should any powder at all exitthrough the air exit holes, this powder will only correspond to aninsignificant percent of the smallest particles. On the other hand, theair will readily expand out through the holes, particularly as the innerrestriction increases the counter-pressure in the inner tube and thusassists said expansion. Neither are the holes 14 and 29, 30 respectivelyin the inner tube particularly critical, although they should, however,be found relatively close to the inner constriction.

It is nevertheless important with respect to optimum efficiency that allholes and cavities in the nozzle balance one another.

It will be understood that many modifications are possible within thescope of the invention defined in the accompanying Claims. For instance,instead of holes in the side of the inner tube, there may be arranged acircular grating that is adapted to allow air to enter but not powderparticles. Although the nozzle of the illustrated embodiments has beenshown to include a protective sleeve, it is possible to produce thecomponent parts of the protective sleeve in one piece with theconcentric tubes. However, the protective sleeve enables simplemanufacture, because it can be produced in one piece and sealinglyfastened to the outer tube 11. The tube 11 can be readily cut off at thebeginning of the expansion channel. Holes 14 and 29, 30 can also bereadily formed, as can also the constriction in at least the embodimentsshown in FIGS. 3 and 4, including the design of the orifices 19, 23 and28.

What is claimed is:
 1. A surface treatment nozzle for generating (a) asurface treatment jet that comprises a suspension of surface treatmentmaterial and gas and (b) a liquid-containing surrounding jet forpreventing dusting, wherein the velocity of the surface treatment jet isgreat than the velocity of solely liquid, and wherein the surfacetreatment jet is conveyed in an inner tube (13; 31) and the liquid isconveyed in a channel (12) defined between the inner tube and a tube(11) that surrounds said inner tube concentrically, the nozzle furthercomprising a mixing arrangement (14, 15, 16; 22; 29, 30, 25) for mixingthe liquid with gas upstream of a nozzle outlet and imparting to theliquid/gas mixture a velocity of the same order of magnitude as thevelocity of the surface treatment jet at said outlet.
 2. The surfacetreatment nozzle according to claim 1, wherein the mixing arrangementincludes an internal outlet from the liquid conducting channel (12), anddischarge means (14; 20, 30) for delivering a part of the gas in thesurface treatment jet as gas to be mixed with the liquid in an amountsuch that the liquid/gas mixture will have the desired velocity.
 3. Thetreatment nozzle according to claim 2, wherein the mixing arrangementincludes a liquid/gas mixture expansion channel (15) external of saiddischarge means.
 4. The surface treatment nozzle according to claim 2,wherein the mixing arrangement includes an at least internalconstriction (16; 25) in said inner tube downstream of the dischargemeans (14; 29,30).
 5. The surface treatment nozzle according to claim 2,wherein the inner tube (13; 31) is circular at least at the nozzleoutlet and has a diameter which provides space for a surrounding flow ofliquid/gas mixture through an apertured (18; 20) area around the orifice(19; 23) of the inner tube.
 6. The surface treatment nozzle according toclaim 5, wherein the apertured area around the inner tube orifice (19)has the form of a ring of drilled holes (18).
 7. The surface treatmentnozzle according to claim 5, wherein the apertured area around the innertube orifice (23) has the form of a central irregular but symmetricalhole (20) that includes wall parts which give internal support to theorifice (23) of the inner tube.
 8. The surface treatment nozzleaccording to claim 2, wherein the inner tube (13; 31) carrying thesuspension of surface treatment material and gas has at least at theoutlet a generally polygonal orifice (28) containing plural corners andthe orifice has a central round hole (27) whose diameter is adapted tosupport the corners and therewith provide space for a surrounding flowof liquid/gas mixture through apertures around the inner tube orifice(28).
 9. The surface treatment nozzle according to claim 2, wherein thesizes and forms of the discharge means, the expansion channel, the innerconstriction and the apertures for the outlet of the liquid/gas mixtureare balanced relative to one another to provide the same order ofmagnitude between the velocities of the suspension of surface treatmentmaterial and gas and the liquid/gas mixture.
 10. The surface treatmentnozzle according to claim 1, wherein the gas is air and the surfacetreatment material is a polishing material.
 11. A surface treatmentnozzle for generating a surface treatment jet that includes a suspensionof surface treatment material in a gas and separates a liquid-containingjet that surrounds the surface treatment jet, the nozzle comprising: aninner tube conveying the suspension of the surface treatment material inthe gas; an outer tube surrounding said inner tube and defining achannel between said inner and outer tubes, a liquid for theliquid-containing jet being conveyed through the channel, wherein avelocity of the liquid in the channel is less than a velocity of thesuspension conveyed through said inner tube; an outlet for the surfacetreatment jet and the separate liquid-containing jet that surrounds thesurface treatment jet; and mixing means for mixing the liquid from thechannel with the gas from the inner tube upstream of said outlet and forimparting to the mixture of the liquid and the gas a velocity of thesame order of magnitude as the velocity of the surface treatment jet atsaid outlet.
 12. The nozzle of claim 11, wherein said mixing meanscomprises an opening through a wall of said inner tube and aconstriction inside side inner tube downstream of said opening.
 13. Thenozzle of claim 11, wherein said outlet comprises a central openingthrough which the surface treatment jet is expelled and plural holesaround said central opening through which the liquid-containing jet isexpelled, said central opening communication with an interior of saidinner tube and said plural holes communicating with an exterior of saidinner tube.
 14. The nozzle of claim 11, wherein said outlet comprises acentral opening through which the surface treatment jet is expelled andpolygonal opening around said central opening through which theliquid-containing jet is expelled, wherein walls of said polygonalopening support said inner tube at said outlet, said central openingcommunication with an interior of said inner tube and said polygonalopening communicating with an exterior of said inner tube.